The present invention relates to a method for continuously wrapping products.
The present invention is advantageously used in the wrapping of foodstuffs, such as chocolates and similar products, to which the following description refers, but without thereby restricting the scope of the inventive concept.
In wrapping machines, a succession of products is positioned at regular intervals and fed in an orderly manner along a given path to a pick-up station, where the products are gripped by transfer means and fed firstly to a feed station, in which a sheet of wrapping material is associated with each product and, gradually, through a succession of folding stations, designed to form a closed wrapper around each product to be wrapped.
The products are normally fed to the pick-up station by an infeed conveyor, whilst the transfer means normally consist of a rotary conveyor equipped with a plurality of peripheral pick-up grippers, which move towards the conveyor in order to pick up the products in succession and transfer them to a first wrapping drum.
The first wrapping drum rotates about an axis of rotation and has a plurality of peripheral pick-up units, designed to pick up the products and feed them through the feed station and along a folding station in which each sheet is partially wrapped around the related product to form a wrapper which is substantially folded in a U-shape.
The sets consisting of the products and the related sheets are then transferred, at a transfer station, to a second wrapping drum, whose axis of rotation is parallel with the axis of rotation of the first drum. The second wrapping drum, in turn, has a plurality of peripheral pick-up units, each consisting of a pair of jaws set opposite one another, projecting radially away from the drum and arranged symmetrically relative to an axis which is substantially radial relative to the drum. Said jaws are designed to follow a substantially circular path about the axis of rotation of the second drum, in order to feed the sets consisting of the products and sheets through the succession of folding stations.
The folding operations to which each sheet folded into a U-shape must be subjected in order to obtain a closed wrapper surrounding the product envisage a first step in which each of the two sides of the sheet projecting beyond the corresponding side of the product are folded, thus further folding the sheet of wrapping material, which assumes the form of a box-shaped, substantially parallelepiped intermediate wrapper inside whose top portion, facing the second drum, the product is housed, whilst the opposite part, the bottom, is open and consists of four side flaps. The side flaps project away from the drum and away from a bottom surface of the product. Pairs of the side flaps are substantially opposite to and parallel with one another and parallel with the axis of symmetry of the pick-up jaws and, specifically, two of the side flaps are parallel with the plane in which the second drum lies and with the circular path.
The intermediate wrapper must then be subjected to a series of folding operations in order to obtain a closed wrapper. Firstly, each of the first two opposite flaps, parallel to the placement plane of the aforementioned circular path, are squarely folded so as to form two substantially rectangular tabs placed in direct contact with the bottom surface of the product and usually partly overlapping, and, for each of the other two second flaps which are parallel to each other and perpendicular to the first flaps, two corresponding triangular end portions are also folded, in such a way as to change the shape of the second flaps, which assume a substantially triangular shape to form a pair of parallel wings substantially perpendicular to the bottom surface of the product. These wings are then folded over each other to close the wrapper.
The folding of the above mentioned wings, which are substantially perpendicular to the bottom surface of the product, is usually performed by a movable folder whose jaws, as they move along the feed path, squarely fold one of the two wings until it is in contact with the tabs which are lying flat against the bottom surface of the product, while a fixed folder located along the path intercepts and squarely folds the other wing until it is in partial contact with the previous wing.
This folding method has the disadvantage that, if the wrapper has to be closed by gumming the wing that is folded squarely over the other, the gumming operation cannot be done properly in synchrony with the other folding steps and without stopping the productxe2x80x94sheet of wrapping material sets during the wrapping cycle.
This constitutes a drawback particularly in the latest-generation wrapping machines which are designed to operate continuously to increase productivity.
Besides slowing down the wrapping cycle, there are also more chances that the wrapper which has just been folded and closed over the product will open again, especially when the wrappers are made from elastic materials that do not easily keep their folds, thus resulting in a relatively high number of finished products being rejected when they are fed out of the machine to a receiving unit.
The aim of the present invention is to provide a method for continuously wrapping products which allows the triangular wings of a partial wrapper to be folded in such a way that the product B sheet of wrapping material sets do not need to stop and in such a way that an adhesive can be applied by a gumming unit to one of the wings so as to keep the finished wrapper properly closed.
Accordingly, the present invention provides a method for continuously wrapping products, characterized in that it comprises the following steps: continuously feeding, at a first defined speed, along a first path and in a first given direction, a succession of products and the corresponding sheets of wrapping material at least partially wrapped around the products to form an intermediate wrapper having a first and a second wing that are substantially transversal to the plane in which the first path lies, project from a surface of the products and are located on opposite sides of the product; folding the first wing towards said product surface and folding the second wing away from the surface using a first folding device that cooperates with the first and second wings as the intermediate wrapper and the product move forward continuously along an intermediate folding portion of the first path; gumming at least one portion of the second wing; folding back the second wing towards the product surface until its gummed portion comes into contact with the first wing, using a second folding device that cooperates with the second wing as the intermediate wrapper and the product move forward continuously along the intermediate folding portion.
The present invention also relates to a device for continuously wrapping products characterized in that it comprises, along a portion of a wrapping machine equipped with a frame and a wall, a wrapping device comprising means for continuously feeding at a first defined speed, along a first path and in a defined first direction, a succession of products and the corresponding sheets of wrapping material at least partially wrapped around the products to form an intermediate wrapper having a first and a second wing that are substantially transversal to the plane in which the first path lies, project from a surface of the products and are located on opposite sides of the product; a first folding device that cooperates with the first and second wings as the intermediate wrapper and the product move forward continuously along an intermediate folding portion of the first path and that is designed to fold the first wing towards said product surface and to fold the second wing away from the surface; a gumming device designed to apply an adhesive to at least one portion of the second wing; a second folding device that cooperates with the second wing as the intermediate wrapper and the product move forward continuously along the intermediate folding portion and that is designed to fold the second wing towards the product surface until its gummed portion comes into contact with the first wing.